The objective of this work is to understand the mode of action of colchicine. Colchicine is a drug with antimitotic, antigout and antitumor properties. It interacts with microtubule protein found in a variety of different cells. It is widely used in cytology. By single crystal X-ray diffraction the 3-dimensional structures of a number of colchine derivatives will be determined. Changes in molecular conformation will be correlated with biological activity to discover what structural parameters determine activity.